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Loudoun Raw Water Engineering Report

Gannett Fleming charts 30-Year plan with preliminary designs for $130 million engineering improvements in Washington D.C. area.
  • Loudoun Raw Water Engineering Report – Gannett Fleming

    Water model simulates river flow and withdrawal dynamics for Potomac River Water Supply Project.

Loudoun Water

Ashburn, Virginia

Our Role
Report, Preliminary Design, Cost Analysis, Client Workshops.

60,000 water service connections
7 months
  • A 30-year plan to address 40 mgd water supply deficit
  • Enhancements to Potomac River Water Supply Program concepts
  • Preliminary complete designs for $130 million system components.

Challenged to satisfy complex safe drinking water requirements, Loudoun Water needed to expand its water resources and address a projected 40 mgd water supply deficit. To meet water customer demands in Loudoun’s Washington, D.C., service area, Gannett Fleming prepared a comprehensive preliminary engineering report on the Loudoun Water raw water supply system that provided options and established a clear path forward.

Consistent with Loudoun Water’s Potomac Water Supply Program goals, Gannett Fleming’s 2012 report evaluated safe yield, design criteria, treatment options, construction costs, and commissioning efforts. The report also outlined a Master Plan to guide Loudoun Water facility development, phasing, and expansion through 2040, while providing customers with a safe and reliable raw water supply source.

What We Did

Completed on a fast-track schedule in seven months, Gannett Fleming’s raw water supply engineering report outlined surveying, subsurface investigations, safe yield modeling, Potomac River computational fluid dynamics modeling, and client workshop considerations. Our raw water and treatment alternatives included a new Potomac River intake and pump station; transmission mains from the river to retired quarries for water storage and use during drought or poor water quality periods; a pump station and transmission main from the quarries to a new water treatment plant; and a finished water transmission main to a distribution system.

Contained within the report, Gannett Fleming programmed a custom daily flow computer model to simulate the proposed raw water supply system daily operation through a continuous 79-year hydrologic period. Our model and analyses anticipated permit, site-specific, and operating conditions considering Virginia Department of Environmental Quality requirements.

Key Features

  • Cost analysis focused on long-term client savings
  • Predictive modeling
  • Raw water infrastructure design alternatives
  • Safe yield analysis.

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